1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, more particularly to an electrophotographic photosensitive member comprising a photosensitive layer containing a disazo pigment having a specified chemical structure. The present invention also relates to an electrophotographic apparatus and a facsimile machine employing the photosensitive member
2. Related Background Art
Known organic photoconductive substances used for electrophotographic photosensitive members include photoconductive polymers typified by poly-N-vinylcarbazole, low-molecular organic photoconductive substances like 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, and combinations of such an organic photoconductive substance with a dye or a pigment.
Electrophotographic photosensitive members employing an organic photoconductive substance have advantages that the photoconductive members are producible with extremely high productivity at a relatively low cost, and that the color sensitivity thereof is arbitrarily controlled by selecting the dye or the pigment to be used. Therefore, organic photoconductive substances have comprehensively been investigated. Recently, function-separation types of photosensitive members have been developed which have a lamination structure comprising a charge-generating layer containing an organic photoconductive dye or pigment and a charge-transporting layer containing aforementioned photoconductive polymer or a low-molecular organic electroconductive substance, whereby the disadvantage of conventional organic electrophotographic photosensitive members such as low sensitivity and low durability have been remarkably alleviated.
Among organic photoconductive substances, many azo dyes have superior photoconductivity generally. Moreover, selection of combinations of an azo component and a coupler component readily gives various properties of the compound. Accordingly, many compounds have been disclosed as organic photoconductive substances, for example, in Japanese Patent Application Laid-Open Nos. Sho-60-131539, Hei-1-312550, etc.
Recently, to meet the demand for higher picture quality and higher durability, electrophotographic photosensitive members are being investigated which have a higher sensitivity and better electrophotographic characteristics even during repeated use.